This analysis project is a longitudinal investigation of early childhood lower respiratory illness (LRI) and patterns of lung growth. Its goal is to analyze an existing electronic dataset generated by an 18-year study (1972-1990) of a population of 102 Black children followed from birth at the Frank Porter Graham Child Development Center. This dataset is of unique value because it includes comprehensive respiratory illness data collected on-site during the children's tenure in the Center's daycare facility and spirometric data collected longitudinally from 3 to 13 years of age. Furthermore, the measurements are for children in a racial group for whom limited cross-sectional or longitudinal spirometric data are available. The proposed longitudinal analyses have two primary objectives. The first is to characterize patterns of functional lung development in Black children from 3 to 13 years of age and relate these patterns to potentially influential factors such as (a) wheezing and non-wheezing associated LRI experience during the infant (ages 0-2) and preschool (ages 2-5) years, (b) ages of occurrence of first and subsequent LRI episodes, and (c) RSV etiology of LRI. Potentially confounding factors include prenatal and childhood exposure to environmental tobacco smoke and allergies. The second objective is to determine the degree to which spirometric parameters "track" for individual children and for populations of children over the interval from 3 to 13 years of age. This objective requires assessment of the degree to which spirometric evaluations during the preschool years are predictive of later lung function. The proposed statistical analyses for achieving these objectives will use recently developed statistical methods based on the general linear mixed model. By design, these methods for longitudinal data can handle unbalanced data with missing values, can incorporate time-varying covariates, and provide more exact to which the level of lung function of individual children is maintained relative to that of other study children and will determine the value of preschool spirometric measurements as predictors of levels of spirometric performance during later childhood and adolescence. These analyses will utilize methods developed recently by Stewart, Pekow, Burchinal, and Helms (1991) that are unique in that they are designed to handle incomplete, inconsistently-timed data as well as complete, balanced data. Completion of the proposed hypothesis tests and analyses will improve our knowledge of patterns of functional lung development during childhood and factors that influence both relative level and growth rate of lung function in Black children and offer new understanding of the predictive value of spirometric tests of lung function performed at an early age.